Liquid oxygen converter



w. A. WILDHACK 2,580,710

LIQUID OXYGEN CONVERTER- Jan. 1, 1952 Filed Feb. 15, 1946 2 SHEETS-SHEET l EVAPORATOR FLASH 1952 w. A. WILDHACK 2,580,710

LIQUID OXYGEN CONVERTER Filed Feb. 13, 1946 2 SHEETS-SHEET 2 H9 4 W////dm A M/dbao Patented Jan. I, 1952 UNITED STATES PATENT OFFICE (Granted under the act of March 3, 1883, as amended April 30, 1928; 370 0. G. 757) 18 Claims.

This invention relates to liquid oxygen converters particularly to such converters for systems in which an automatically or manually controlled cycling evaporator may be used for building up pressure by compressing gas over the liquid. A similar design can be used to force gas through the liquid to warm it.

The object of this invention is to provide a system for building up pressure in a liquid oxygen converter by using an automatically or manually cycled evaporator to obtain or maintain the pressure of delivery.

A further object is to construct apparatus for use in a liquid oxygen or other liquifled gas container 01' converter. for efllcient handling in dispensing such liquid or gas at desired pressures either intermittently or continuously and the rapid attainment of the desired pressures.

Other and more specific objects will become apparent in the following detailed description of the apparatus, having reference to the ac companying drawings, wherein:

Fig. 1 illustrates schematically one model in which a cyclic operation was attained;

Fig. 2 is a schematic diagram of another modification with an optional circuit for warming the entire mass of liquid before using the converter;

Fig. 3 is a-schematic diagram of another modification showing a simpler manually controlled cyclic evaporator: and

Fig. 4 is an end view of the lower reservoirevaporator connection showing the restriction L.

The essential characteristic of one form of this invention is an automatically cycling evaporator, in which liquid is drawn from the container into an auxiliary reservoir, and when the reservoir is full, into a flash evaporator, where sudden evaporation of some of the liquid causes a pressure-closing valve to close. Evaporation of the liquid from the auxiliary reservoir in the reservoir or in an evaporating coil then forces gas into the container above the liquid, building up the pressure, or'into the liquid, warming it by condensation.

The schematic diagram shown in Fig. 1 illustrates the system first tried in which a cyclic operation was attained. The component parts are identified in the diagram as follows:

The liquid oxygen container has a gas phase connection to a pressure gage K and pressure relief valve J. and a liquid phase connection through a tube A to a main evaporator I and delivery valve H and also through a check valve D and reservoir evaporator E to a flash evaporator G, then through a loaded check valve F to the as phase connection. The flash evaporator G is also connected through a pressure closing valve C to a manual valve B opening to the atmosphere.

The term evaporator unless limited by modifying phraseology is intended to refer to either the reservoir or flash evaporators or both of these units. The term "flash evaporator is defined as a liquid evaporator constructed with excessive evaporating capacity so as to operate with relatively high speed.

After filling the container at atmospheric pressure, it is usually necessary to wait a few minutes for the pressure in the container to rise sufflciently to force liquid up the tube A when the pressure starting valve B is opened. If filling is done under some pressure, this delay may be avoided; or suction may be applied to the outlet of valve B to start the cycle. The subsequent operation is as follows:

The pressure being low, the pressure-closing .valve C is open. Thus when the manual valve B is opened, liquid is forced up through the tube A, past the check valve D into the evaporator reservoir E. Gas from the vapor phase is prevented from escaping by the check valve F. Any liquid which evaporates during the filling of the reservoir passes out through the pressure-closing valve and the open manual valve .to the atmosphere. When the reservoir E is filled, liquid oxygen spills over into the flash evaporator G, where it evaporates rapidly, creating a high pressure which causes the pressure closing valve to close. The check valve D prevents the liquid from returning down the tube A, but the check valve F permits the gas to enter the space above the liquid. The liquid in the reservoir E continues to evaporate, at a rate determined by the heat absorption, and is forced into the container, compressing the gas above the liquid and raising the pressure.

When the liquid in E is evaporated, the pressure falls, the pressure closing valve 0 opens, and the cycle repeats again and again until the pressure is high enough so that the pressure closing valve C remains closed.

The gas compressed over the liquid will condense, in part, forming a layer of liquid at a temperature in equilibrium with the higher pressure. This liquid layer will cool by heat exchange with the lower cooler layer. so that further condensation will occur, slowly lowering the pres.- sure, and causing infrequent repetition of the cycle.

Two different types of operation of the pressure-closing valve C have been used. In one, the

valve is preset to close at the desired operating pressure. Valve B is then chosenso that when opened, the restriction to flow is such that a high pressure is created in valve C by the flash" evaporation of the liquid in G.

In the other method, the valve C is manually adjustable and is set to close at a relatively low pressure for the first cycle, a somewhat higher pressure for the next cycle, and so on until the desired pressure is attained; then the adjustment is not changed further and subsequent cycling occurs automatically to maintain the pressure. I

Particularly in thefirst method, loading the check valve F, or placing a restriction in the hose near it, was found desirable to ensure maintenance of pressure on the valve C during the evaporation part of the'cycle. The use of a pressureopening valve near F, set to open at a pressure slightly below the closing pressure for valve C, would be better.

In the latter method, the valve B can be omitted since valve C can be closed by the manual adjustment. Some restriction is desirable in the outlet, particularly if the flow capacity of the valve C is large, to ensure that the pressure will become high enough to close the valve when flash evaporation occurs.

With the pressure at the desired value thus obtained and maintained, gas at this pressure is delivered by the converter as required when the supply valve H is opened, the liquid flowing up the tube A, and into the main evaporator coil I, where it evaporates and is warmed to near ambient temperatures.

Fig. 2 is a schematic diagram of another form of converter with provision of an optional circuit for warming the entire mass of liquid before using the converter, if desired.

The designations of the parts which are similar to those used in the apparatus of Fig. 1 are the same as in that figure. The reservoir E however is insulated and has a restricted opening L in the bottom to the flash evaporator G besides the overflow connection in the top. A pressure evaporator coil P is also provided between the insulated reservoir and the loaded checlc valve F as shown, a.

conduit being inserted between the junction of the reservoir with check valve D and with this coil P, and the top of the main evaporator coil I through a manual valve M and check valve 0. The lower end of tube A may be provided with a bubbler N, although this is normally not necessary.

The operation in filling the reservoir is as in the mode described above. When the manual valve B at the outlet of the pressure closing valve C is opened, gas flows out through the pressure closing valve, liquid fills the reservoir E and then spills into the flash evaporator G, where the sudden evaporation creates a pressure suflicient to close the pressure closing valve C. In this design, provision is made for maintaining pressure in the insulated reservoir by using the flash evaporator G also as a pressure-building evaporator. Liquid flows slowly through the restricted bottom connection L from the reservoir to the evaporator, evaporates and forces warmed gas back into the space above the liquid in E, increasing the pressure and forcing the liquid back up the central tube. The check valve F in the pressure evaporator circuit is loaded to a greater value than valve so that flow is preferentially through the check valve 0 into the main evaporator I if the manual valve M in the upper line is open.

The liquid evaporates in the main evaporator coil and the warmed gas is forced through the tube A which extends to the bottom of the liquid, warming the liquid as it condenses. The bubbler N (a coil of tubing with fine holes, or a porous wall) is recommended only when it is desirable to minimize the tendency for the warm gas bubbles to rise into the gas phase without cooling, thereby forming a warm layer on top of the liquid, and creating a pressure in excess of that corresponding to the average temperature of the liquid.

When the reservoir is empty, the pressure in that part of the system falls, enough for the pressure closing valve C to open. The liquid flows up the tube A, through the check valve D, being prevented from flowing in the other circuits by the check valves F and O, fills the reservoir and the cycle repeats.

For simplest manual operation the reservoir E may be vented directly through the manual valve 13, omitting the pressure closing valve C. The evaporator G may also be omitted, particularly if the reservoir is poorly insulated; heat absorbed by the liquid in the reservoir will increase its pressure and force it through the liquid warming circuit. In a preferred construction, however, the evaporator G may be made to surround the reservoir E.

If more pressure control of the pressure is desired, the restriction in the connection L may be replaced by a pressure closing valve, so that pressure in the pressure-building circuit is not maintained above a desired value. The operation of the evaporator G is then in accordance with the principles followed in co-pending applications, Serial No. 645,692, filed February 5, 1946, now Patent No. 2,576,985, December 4, 1951, and Serial No. 689,353, flied August 9, 1946, now Patent No. 2,576,984, December 4, 1951.

If the manual valve M is closed to prevent flow through the liquid-warming circuit, the pressure generated in the reservoir forces liquid through the pressure evaporator and past the loaded check valve F into the space above the liquid. This will build up the pressure rapidly, but as the compressed gas condenses on the surface of the liquid and conducts heat to the liquid below, the pressure will diminish. When the pressure has dropped sumciently to open the pressure closing valve, another cycle will begin.

If the usual mode of operation contemplated is to use the liquid-warming circuit, a relatively large reservoir is desirable, since the loss of gas during filling is largely that due to cooling of the circuit and may therefore not be much greater for a large reservoir than for a small one. The number of cycles of operation will obviously be less for a large reservoir. However, a large reservoir may be wasteful when used only for maintaining pressure by forcing gas into the space above the liquid, since excessive pressures may be generated and force gas out the relief valve. The addition of a pressure closing valve in the upper connection between the reservoir and the flash evaporator, set to close at a pressure somewhat above that required to stop filling, would limit the pressure generated in the reservoir. The rate of evaporation in either of the evaporating circuits could then be controlled by appropriate restrictions. Since the rate of evaporation desired for maintaining pressure may be only a liter or so per minute, whereas the rate desired for building up pressure initially by warming the liquid might be several hundred liters per minute, it is apparent that the same rate of efilux of liquid from the reservoir may not be desirable under the two conditions. If the reservoir is small, the pressure evaporator may be able to evaporate its entire charge without increasing the pressure to excessive values.

In applications where delivery can be interrupted at will, the pressure warming circuit shown can be used alone. When delivery must be continuous, once started, the pressure evaporator circuit may be needed, since the liquid warming process will usually not warm the liquid uniformly, and the pressure will decrease as heat interchange occurs.

Of course, if a large variation in supply pressure can be tolerated, it may be possible to warm theliquid sufliciently to give the desired final equilibrium value, with much higher pressures initially.

It may thus be seen that the characteristic feature of the oxygen converters described above is a cyclic evaporator for rapid attainment of operating pressure.

For many applications the automatic cycling is not essential, and manual control of the cycling is sufiicient. A modified form of converter omitting the automatic cycling feature and making the system much simpler, is shown in Fig. 3. In the operation of this form, the manually operated shut-off valve B is opened to allow the small reservoir E to be partly or entirely filled with the liquid forced up into it through the tube A and check valve D by the residual pressure in the gas phase of the container. Valve B is then closed and the evaporation of the liquid in reservoir E gradually builds up the pressure as heat is absorbed from the atmosphere and drives the warmed liquid in the reservoir through the warming and evaporating coil I into the liquid phase in the container to ultimately raise the pressure in the gaseous phase and the temperature of the liquid phase sufficiently to provide for a considerable supply of the oxygen in gaseous form when the supply valve is opened. When the supply pressure becomes too low, the supply valve is closed and a new pressure building cycle is again initiated by opening the manually operated valve B;

Many obvious modifications may be made in the constructions and arrangements shown herein without departing from the spirit and scope of the present invention, as defined in the appended claims.

The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

What is claimed is:

1. Pressure build-up apparatus for liquid oxygen converters comprising a liquid oxygen container, a pressure build-up circuit having a reservoir evaporator connected to the liquid phase of said container through a check valve, a flash evaporator, a conduit from said reservoir to said flash evaporator, a conduit connected between said container and said flash evaporator for conducting the gas generated under pressure in said flash evaporator to said container through a non-return check valve, and a pressure closing valve connected to said flash evaporator and opening to the atmosphere for cyclic operation to cause liquid to flow into said reservoir evaporator and then into saidflash evaporator whenever the pressure therein falls below the pressure in said container.

2. Pressure build-up and supply apparatus for liquid oxygen converters comprising a liquid oxygen container having a cap fitting, a short tube passing through said cap fitting into the gas phase in said container, a long tube passing through said cap fitting and extending into the liquid phase in said container, a pressure buildup circuit including a check valve for controlling flow out of said long tube, a reservoir evaporator for receiving said flow, a fiash evaporator connected to an overflow conduit from said reservoir evaporator and by another conduit through a loaded check valve to said short tube for conducting thegas generated under high pressure in said flash evaporator to the gas phase in said container, a pressure closing valve connected to said flash evaporator and opening to the atmosphere for causing flow of liquid into said reservoir evaporator and from there by overflow into said flash evaporator whenever the pressure in said flash evaporator falls below the pressure in said container, and a supply circuit having an evaporator and warming coil and a supply valve connected to said long tube.

3. Pressure build-up and supply apparatus for liquid oxygen converters comprising a liquid oxygen container, a pressure build-up circuit having an insulated reservoir with a tube extending to the bottom of said reservoir connected to the liquidphase in said container through a check valve for receiving liquid oxygen from said container, a flash evaporator connected by a free passage to the top of said reservoir and by a restricted passage to the bottom of said reservoir, a pressure closing valve opening to the atmosphere and connected to said flash evaporator for causing flow of liquid oxygen from said container into said reservoir whenever the pressure in said flash evaporator falls below the pressure in said container, a pressure evaporator connected between said tube in said reservoir and the gas phase in said container through a loaded check valve, a

off valve connected at its top, a tube extending from the liquid phase in said container through a check valve to the bottom of said reservoir for delivering liquid oxygen thereto whenever said cut-off valve is opened, a warming and evaporating coil connected at one end to said tube and at its other end to a delivery valve, a conduit extending from the bottom of said reservoir to said other end of said warming and evaporating coil, and a check valve in said conduit for controlling flow of oxygen from said reservoir to said coil.

5. A pressurizing apparatus for liquefied gas systems comprising an insulated container, an evaporator unit for developing pressure in said apparatus, a tube connecting the liquid phase section in the container to said evaporator unit for conveying liquid thereto, a check valve in said tube, a valve to the atmosphere for venting the evaporator unit, and a return conduit containing a check valve connecting the evaporator unit to said tube for delivering the compressed dis charge from said evaporator unit below the surface or the liquid.

6. A cyclic prcssurizing apparatus for liquefied gas systems comprising an insulated container. an evaporator. a tube from the bottom of the liquid in the container connected to said evaporator, a one-way check valve in said tube for passing liquid to said evaporator, an automatic pressure-closingvent valve to the atmosphere connected to said evaporator, said pressure-closing valve being open at low pressures and closed in response to the pressure rise above a preset value, and a return conduit containing a check valve connecting the evaporator to the container.

7. A pressurizing apparatus for liquefied gas systems comprisin an insulated container, an insulated reservoir, a tube from the bottom of the liquid in the container connected to said insulated reservoir, a check valve in said tube, an uninsulated evaporator connected to said insulated reservoir, a valve connected to the evaporator for venting the evaporator to the atmosphere, and a return conduit containing a check valve connecting the reservoir to the container.

8. A pressurizing system for liquefied gas systems comprising an insulated container, an insulated reservoir.a tube from the bottom of the liquid in the container connected through a check valve to said insulated reservoir, an uninsulated evaporator connected by a free passage to the top of said reservoir and by a restricted passage to the bottom of said reservoir, a valve to the atmosphere for venting the evaporator. and a return conduit containing a check valve connectlllp; the reservoir to the container.

9. A pressurizing system for liquefied gas systems comprising an insulated container, an insulated reservoir, a tube from the bottom of the liquid in the container connected through a check valve to said insulated reservoir, an uninsulated evaporator adjoining said reservoir and connected to it by a hole at the bottom of the reservoir and a hole at the top of the reservoir, a valve to the atmosphere for venting the evaporator. and a return conduit containing a check valve connecting the reservoir to the container.

10. A pressurized system for liquefied gas systems comprising an insulated container, an insulated reservoir, a tube from the bottom of the liquid in the container connected through a check valve to said insulated reservoir, an uninsulated evaporator adjoinin said reservoir and connected to it by a restricted opening at the bottom of the reservoir and a hole at the top of the reservoir, a valve to the atmosphere for venting the evaporator, and a return conduit containin a check valve connecting the reservoir to the container.

11. A pressurized apparatus for liquefied gas systems comprising an insulated container, an evaporator, a tube from the bottom of the liquid in the container connected through a check valve to said evaporator, a valve to the atmosphere for venting the evaporator, a return conduit containing a check valve connecting the evaporator to the container, and a supply circuit having an evaporatin and warming coil and a supply valve connected to the liquid phase of the container.

12. A press-urizing system for liquefied gas systems comprising an insulated container, an insulated reservoir, a tube from the bottom of the liquid in the container through a check valve, which prevents return of gas to the container, to said insulated reservoir, an evaporator for developing pressure in the apparatus, a pressureclosing valve connected to the evaporator and normally open to the atmosphere for causing liquid to flow into the reservoir whenever the pressure therein falls below the pressure in said container, a warming coil, a one-way valve, and conduit means for conducting fluid from said reservoir through said one-way valve and warmin coil to the containers, whereby the warmed gas causes an increase in pressure in the container, the cycle being repeated until the pressure in the container is stable above a predetermined value.

13. The apparatus as described in claim 18, the return tube containing the valve of higher loaded value having an auxilliary line evaporator connected in series therewith.

14. The apparatus as described in claim 12 including gas distributing means at the open end of said tube within said container.

15. The pressure build-up apparatus as defined in claim 1 and a supply circuit having an evaporating and warming coil and a supply valve connected to the liquid phase of said container.

16. The pressure build-up and supply apparatus of claim 3 and a bubbler interposed in said supply circuit connection to the liquid phase of the container for facilitatin the warming of the entire volume of liquid in said container to an even temperature whenever gas from the'build- .up circuit through the evaporating and warming coil is passed mto said container.

1'7. A pressurizing apparatus for liquified gas systems comprising a container, an evaporator, a tube extending from the liquid section in the container to said evaporator, a check valve in said tube, an automatic pressure-loaded valve open to the atmosphere for venting the evaporator below the load pressure of said pressureloaded valve, and a return tube containing a oneway check valve connecting the evaporator to the container.

18. A pressurizin apparatus for liquifled gas systems comprising a container, an evaporator, a tube extending from the bottom of the liquid in the container connected through a check valve to said evaporator, an automatic one-way pressure loaded valve open to the atmosphere for venting the evaporator below the load pressure of said valve, and dual return tubes from the evaporator to the container containing one-way pressure loaded valves closed below the load value, one of said return tube valves being loaded for opening at a higher load value than that of the other return tube valve, the return tube containing the lower loaded valve being connected to the liquid phase section of the container and the return tube containin the higher loaded valve being conneced to the gas phase section of the container.

WILLIAM A. WILDHACK.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,853,983 Leach Apr. 12, 1932 2,037,673 Zenner Apr. 14, 1936 2,257,897 Zenner et a1. Oct. 7, 1941 2,464,835 Thayer et al Mar. 22, 1949 FOREIGN PATENTS Number Country Date 829,961 France July 18, 1938 

